CHAPTER III. 



THE AQUARIUM. 



The successful treatment of aquatic plants and 

 animals, in the confined space of a glass Aqua- 

 rium, depends entirely upon the discovery that 

 there exists in ISTature a self-adjusting balance be- 

 f tween the supply of oxygen created in water, with 

 ; the quantity consumed by aquatic animals. And 

 it became equally necessary to know the means 

 by which that supply was continually generated. 

 Without the knowledge of these facts, and the 

 principles by which they are regulated, it would 

 have "'been impossible to establish such a marine 

 Aquarium as that we may now any day examine in 

 the E;egent's Park ; where, in a few glass tanks of 

 very moderate size, we may see examples of some of 

 the most curious forms of animal and vegetable life 

 peculiar to the depths of the ocean — forms so singu- 

 lar, that their first exhibition created a sense of 

 wonder little less intense than that which must have 

 been caused, long years ago, by the first public dis- 

 play of the mountain form of the elephant to the 



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